Prognostic significance and modalities of flow cytometric minimal residual disease detection in childhood acute lymphoblastic leukemia

Prospective use of molecular minimal residual disease for risk stratification in children and adolescents with acute lymphoblastic leukemia : Long-term results of the AIEOP-BFM ALL 2000 trial in Austria

Since 1979 Austrian children and adolescents with acute lymphoblastic leukemia (ALL) have been treated according to protocols of the Berlin-Frankfurt-Münster (BFM) study group. The Associazione Italiana di Ematologia e Oncologia Pediatrica and BFM (AIEOP-BFM) ALL 2000 study was designed to prospectively study patient stratification into three risk groups using minimal residual disease (MRD) on two time points during the patient's early disease course. The MRD levels were monitored by detection of clone-specific rearrangements of the immunoglobulin and T‑cell receptor genes applying a quantitative polymerase chain reaction-based technique. The 7‑year event-free survival (EFS) and overall survival rates for all 608 Austrian patients treated between June 1999 and December 2009 within the AIEOP-BFM 2000 study were 84 ± 2% and 91 ± 1%, respectively, with a median observation time of 6.58 years. Event-free survival for patients with precursor B‑cell and T‑cell ALL were 84 ± 2% (n = 521) and 84 ± 4% (n = 87; p = 0.460), respectively. The MRD assessment was feasible in 94% of the patients and allowed the definition of precursor B‑cell ALL patients with a low, intermediate or high risk of relapse even on top of clinically relevant subgroups. A similar finding with respect to MRD relevance in T‑ALL patients was not possible due to the small number of patients and events. Since this pivotal international AIEOP-BFM ALL 2000 trial, molecular response to treatment has been continuously used with additional refinements to stratify patients into different risk groups in all successive trials of the AIEOP-BFM ALL study group.

Monitoring measurable residual disease in paediatric acute lymphoblastic leukaemia using immunoglobulin gene clonality based on next-generation sequencing

BACKGROUND

Assessment of measurable residual disease (MRD) is an essential prognostic tool for B-lymphoblastic leukaemia (B-ALL). In this study, we evaluated the utility of next-generation sequencing (NGS)-based MRD assessment in real-world clinical practice.

METHOD

The study included 93 paediatric patients with B-ALL treated at our institution between January 2017 and June 2022. Clonality for IGH or IGK rearrangements was identified in most bone marrow samples (91/93, 97.8%) obtained at diagnosis.

RESULTS

In 421 monitoring samples, concordance was 74.8% between NGS and multiparameter flow cytometry and 70.7% between NGS and reverse transcription-PCR. Elevated quantities of clones of IGH alone (P < 0.001; hazard ratio [HR], 22.2; 95% confidence interval [CI], 7.1-69.1), IGK alone (P = 0.011; HR, 5.8; 95% CI, 1.5-22.5), and IGH or IGK (P < 0.001; HR, 7.2; 95% CI, 2.6-20.0) were associated with an increased risk of relapse. Detection of new clone(s) in NGS was also associated with inferior relapse-free survival (P < 0.001; HR, 18.1; 95% CI, 3.0-108.6). Multivariable analysis confirmed age at diagnosis, BCR::ABL1-like mutation, TCF3::PBX1 mutation, and increased quantity of IGH or IGK clones during monitoring as unfavourable factors.

CONCLUSION

In conclusion, this study highlights the usefulness of NGS-based MRD as a routine assessment tool for prognostication of paediatric patients with B-ALL.

Blinatumomab as postremission therapy replaces consolidation and substantial parts of maintenance chemotherapy and results in stable MRD negativity in children with newly diagnosed B-lineage ALL

The bispecific T cell-binding antibody blinatumomab (CD19/CD3) is widely and successfully used for the treatment of children with relapsed or refractory B-cell precursor acute lymphoblastic leukemia (BCP-ALL). Here, we report the efficacy of a single course of blinatumomab instead of consolidation chemotherapy to eliminate minimal residual disease (MRD) and maintain stable MRD-negativity in children with primary BCP-ALL.Between February 2020 and November 2022, 177 children with non-high-risk BCP-ALL were enrolled in the ALL-MB 2019 pilot study (NCT04723342). Patients received the usual risk-adapted induction therapy according to the ALL-MB 2015 protocol. Those who achieved a complete remission at the end of induction (EOI) received treatment with blinatumomab immediately after induction at a dose of 5 μg/m2/day for 7 days and 21 days at a dose of 15 μg/m2/day, followed by 12 months of maintenance therapy. MRD was measured using multicolor flow cytometry (MFC) at the EOI, then immediately after blinatumomab treatment, and then four times during maintenance therapy at 3-month intervals.All 177 patients successfully completed induction therapy and achieved a complete hematological remission. In 174 of these, MFC-MRD was measured at the EOI. 143 patients (82.2%) were MFC-MRD negative and the remaining 31 patients had varying degrees of MFC-MRD positivity.MFC-MRD was assessed in all 176 patients who completed the blinatumomab course. With one exception, all patients achieved MFC-MRD negativity after blinatumomab, regardless of the MFC-MRD score at EOI. One adolescent girl with high MFC-MRD positivity at EOI remained MFC-MRD positive. Of 175 patients who had completed 6 months of maintenance therapy, MFC-MRD data were available for 156 children. Of these, 155 (99.4%) were MFC-MRD negative. Only one boy with t(12;21) (p13;q22)/ETV6::RUNX1 became MFC-MRD positive again. The remaining 174 children had completed the entire therapy. MFC-MRD was examined in 154 of them, and 153 were MFC-MRD negative. A girl with hypodiploid BCP-ALL showed a reappearance of MFC-MRD with subsequent relapse.In summary, a single 28-day course of blinatumomab immediately after induction, followed by 12 months of maintenance therapy, is highly effective in achieving MRD-negativity in children with newly diagnosed non-high risk BCP-ALL and maintaining MRD-negative remission at least during the treatment period.

The Evolving Landscape of Flowcytometric Minimal Residual Disease Monitoring in B-Cell Precursor Acute Lymphoblastic Leukemia

Detection of minimal residual disease (MRD) is a major independent prognostic marker in the clinical management of pediatric and adult B-cell precursor Acute Lymphoblastic Leukemia (BCP-ALL), and risk stratification nowadays heavily relies on MRD diagnostics. MRD can be detected using flow cytometry based on aberrant expression of markers (antigens) during malignant B-cell maturation. Recent advances highlight the significance of novel markers (e.g., CD58, CD81, CD304, CD73, CD66c, and CD123), improving MRD identification. Second and next-generation flow cytometry, such as the EuroFlow consortium's eight-color protocol, can achieve sensitivities down to 10-5 (comparable with the PCR-based method) if sufficient cells are acquired. The introduction of targeted therapies (especially those targeting CD19, such as blinatumomab or CAR-T19) introduces several challenges for flow cytometric MRD analysis, such as the occurrence of CD19-negative relapses. Therefore, innovative flow cytometry panels, including alternative B-cell markers (e.g., CD22 and CD24), have been designed. (Semi-)automated MRD assessment, employing machine learning algorithms and clustering tools, shows promise but does not yet allow robust and sensitive automated analysis of MRD. Future directions involve integrating artificial intelligence, further automation, and exploring multicolor spectral flow cytometry to standardize MRD assessment and enhance diagnostic and prognostic robustness of MRD diagnostics in BCP-ALL.

Diagnostic and therapeutic advances in adults with acute lymphoblastic leukemia in the era of gene analysis and targeted immunotherapy

Acute lymphoblastic leukemia (ALL) is one of the most rapidly changing hematological malignancies with advanced understanding of the genetic landscape, detection methods of minimal residual disease (MRD), and the development of immunotherapeutic agents with good clinical outcomes. The annual incidence of adult ALL in Korea is 300-350 patients per year. The WHO classification of ALL was revised in 2022 to reflect the molecular cytogenetic features and suggest new adverse- risk subgroups, such as Ph-like ALL and ETP-ALL. We continue to use traditional adverse-risk features and cytogenetics, with MRD-directed post-remission therapy including allogeneic hematopoietic cell transplantation. However, with the introduction of novel agents, such as ponatinib, blinatumomab, and inotuzumab ozogamicin incorporated into frontline therapy, good MRD responses have been achieved, and overall survival outcomes are improving. Accordingly, some clinical trials have suggested a possible era of chemotherapy-free or transplantation-free approaches in the near future. Nevertheless, relapse of refractory ALL still occurs, and some poor ALL subtypes, such as Ph-like ALL and ETP-ALL, are unsolved problems for which novel agents and treatment strategies are needed. In this review, we summarize the currently applied diagnostic and therapeutic practices in the era of advanced genetic analysis and targeted immunotherapies in United States and Europe and introduce real-world Korean data.

FCM marker importance for MRD assessment in T-cell acute lymphoblastic leukemia: An AIEOP-BFM-ALL-FLOW study group report

T-lineage acute lymphoblastic leukemia (T-ALL) accounts for about 15% of pediatric and about 25% of adult ALL cases. Minimal/measurable residual disease (MRD) assessed by flow cytometry (FCM) is an important prognostic indicator for risk stratification. In order to assess the MRD a limited number of antibodies directed against the most discriminative antigens must be selected. We propose a pipeline for evaluating the influence of different markers for cell population classification in FCM data. We use linear support vector machine, fitted to each sample individually to avoid issues with patient and laboratory variations. The best separating hyperplane direction as well as the influence of omitting specific markers is considered. Ninety-one bone marrow samples of 43 pediatric T-ALL patients from five reference laboratories were analyzed by FCM regarding marker importance for blast cell identification using combinations of eight different markers. For all laboratories, CD48 and CD99 were among the top three markers with strongest contribution to the optimal hyperplane, measured by median separating hyperplane coefficient size for all samples per center and time point (diagnosis, Day 15, Day 33). Based on the available limited set tested (CD3, CD4, CD5, CD7, CD8, CD45, CD48, CD99), our findings prove that CD48 and CD99 are useful markers for MRD monitoring in T-ALL. The proposed pipeline can be applied for evaluation of other marker combinations in the future.

Tisagenlecleucel utilisation and outcomes across refractory, first relapse and multiply relapsed B-cell acute lymphoblastic leukemia: a retrospective analysis of real-world patterns

Background

Tisagenlecleucel was approved by the Food and Drug Administration (FDA) in 2017 for refractory B-cell acute lymphoblastic leukemia (B-ALL) and B-ALL in ≥2nd relapse. Outcomes of patients receiving commercial tisagenlecleucel upon 1st relapse have yet to be established. We aimed to report real-world tisagenlecleucel utilisation patterns and outcomes across indications, specifically including patients treated in 1st relapse, an indication omitted from formal FDA approval.

Methods

We conducted a retrospective analysis of real-world tisagenlecleucel utilisation patterns across 185 children and young adults treated between August 30, 2017 and March 6, 2020 from centres participating in the Pediatric Real-World CAR Consortium (PRWCC), within the United States. We described definitions of refractory B-ALL used in the real-world setting and categorised patients by reported Chimeric Antigen Receptor (CAR) T-cell indication, including refractory, 1st relapse and ≥2nd relapse B-ALL. We analysed baseline patient characteristics and post-tisagenlecleucel outcomes across defined cohorts.

Findings

Thirty-six percent (n = 67) of our cohort received tisagenlecleucel following 1st relapse. Of 66 evaluable patients, 56 (85%, 95% CI 74-92%) achieved morphologic complete response. Overall-survival (OS) and event-free survival (EFS) at 1-year were 69%, (95% CI 58-82%) and 49%, (95% CI 37-64%), respectively, with survival outcomes statistically comparable to remaining patients (OS; p = 0.14, EFS; p = 0.39). Notably, toxicity was increased in this cohort, warranting further study. Interestingly, of 30 patients treated for upfront refractory disease, 23 (77%, 95% CI 58-90%) had flow cytometry and/or next-generation sequencing (NGS) minimum residual disease (MRD)-only disease at the end of induction, not meeting the historic morphologic definition of refractory.

Interpretation

Our findings suggested that tisagenlecleucel response and survival rates overlap across patients treated with upfront refractory B-ALL, B-ALL ≥2nd relapse and B-ALL in 1st relapse. We additionally highlighted that definitions of refractory B-ALL are evolving beyond morphologic measures of residual disease.

Funding

St. Baldrick's/Stand Up 2 Cancer, Parker Institute for Cancer Immunotherapy, Virginia and D.K. Ludwig Fund for Cancer Research.

Effects of isolated central nervous system involvement evaluated by multiparameter flow cytometry prior to allografting on outcomes of patients with acute lymphoblastic leukemia

Introduction

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains a major strategy to cure patients with acute lymphoblastic leukemia (ALL). The aim of this study was to evaluate whether isolated flow cytometry (FCM)-positive central nervous system (CNS) involvement before allo-HSCT is clinically significant.

Methods

The effects of isolated FCM-positive CNS involvement prior to transplantation on the outcomes of 1406 ALL patients with complete remission (CR) were retrospectively investigated.

Results

Patients were classified into isolated FCM-positive CNS involvement (n=31), cytology-positive CNS involvement (n = 43), and negative CNS involvement (n = 1332) groups. Among the three groups, the 5-year cumulative incidence of relapse (CIR) values were 42.3%, 48.8%, and 23.4%, respectively (P<0.001). The 5-year leukemia-free survival (LFS) values were 44.7%, 34.9%, and 60.8%, respectively (P<0.001). Compared with the negative CNS group (n=1332), the 5-year CIR of the pre-HSCT CNS involvement group (n=74) was higher (46.3% vs. 23.4%, P<0.001], and the 5-year LFS was inferior (39.1% vs. 60.8%, P<0.001). Multivariate analysis indicated that four variables, T-cell ALL, in second complete remission or beyond (CR2+) at HSCT, pre-HSCT measurable residual disease positivity, and pre-HSCT CNS involvement, were independently associated with a higher CIR and inferior LFS. A new scoring system was developed using the following four variables: low-risk, intermediate-risk, high-risk, and extremely high-risk groups. The 5-year CIR values were 16.9%, 27.8%, 50.9%, and 66.7%, respectively (P<0.001), while the 5-year LFS values were 67.6%, 56.9%, 31.0%, and 13.3%, respectively (P<0.001).

Conclusion

Our results suggest that ALL patients with isolated FCM-positive CNS involvement are at a higher risk of recurrence after transplantation. Patients with pre-HSCT CNS involvement had higher CIR and inferior survival outcomes.

Childhood Acute Lymphoblastic Leukemia: Results of the Randomized Acute Lymphoblastic Leukemia Intercontinental-Berlin-Frankfurt-Münster 2009 Trial

PURPOSE

The International Berlin-Frankfurt-Münster (BFM) study group conducted a study on pediatric acute lymphoblastic leukemia (ALL). Minimal residual disease (MRD) was assessed using flow cytometry (FCM), and the impact of early intensification and methotrexate (MTX) dose on survival was evaluated.

PATIENTS AND METHODS

We included 6,187 patients younger than 19 years. MRD by FCM refined the risk group definition previously used in the ALL intercontinental-BFM 2002 study on the basis of age, WBC count, unfavorable genetic aberrations, and treatment response measured morphologically. Patients at intermediate risk (IR) and high risk (HR) were randomly assigned to protocol augmented protocol I phase B (IB) versus IB regimen. MTX doses of 2 versus 5 g/m² every 2 weeks, four times, were evaluated in precursor B-cell-ALL (pcB-ALL) IR.

RESULTS

The 5-year event-free survival (EFS ± SE) and overall survival (OS ± SE) rates were 75.2% ± 0.6% and 82.6% ± 0.5%, respectively. Their values in risk groups were standard risk (n = 624), 90.7% ± 1.4% and 94.7% ± 1.1%; IR (n = 4,111), 77.9% ± 0.7% and 85.7% ± 0.6%; and HR (n = 1,452), 60.8% ± 1.5% and 68.4% ± 1.4%, respectively. MRD by FCM was available in 82.6% of cases. The 5-year EFS rates in patients randomly assigned to protocol IB (n = 1,669) and augmented IB (n = 1,620) were 73.6% ± 1.2% and 72.8% ± 1.2%, respectively (P = .55), while those in patients receiving MTX doses of 2 g/m² (n = 1,056) and MTX 5 g/m² (n = 1,027) were 78.8% ± 1.4% and 78.9% ± 1.4%, respectively (P = .84).

CONCLUSION

The MRDs were successfully assessed using FCM. An MTX dose of 2 g/m² was effective in preventing relapse in non-HR pcB-ALL. Augmented IB showed no advantages over the standard IB.

Flow cytometric assessment for minimal/measurable residual disease in B lymphoblastic leukemia/lymphoma in the era of immunotherapy

Minimal/measurable residual disease (MRD) is the most important independent prognostic factor for patients with B-lymphoblastic leukemia (B-LL). MRD post therapy has been incorporated into risk stratification and clinical management, resulting in substantially improved outcomes in pediatric and adult patients. Currently, MRD in B-ALL is most commonly assessed by multiparametric flow cytometry and molecular (polymerase chain reaction or high-throughput sequencing based) methods. The detection of MRD by flow cytometry in B-ALL often begins with B cell antigen-based gating strategies. Over the past several years, targeted immunotherapy directed against B cell markers has been introduced in patients with relapsed or refractory B-ALL and has demonstrated encouraging results. However, targeted therapies have significant impact on the immunophenotype of leukemic blasts, in particular, downregulation or loss of targeted antigens on blasts and normal B cell precursors, posing challenges for MRD detection using standard gating strategies. Novel flow cytometric approaches, using alternative strategies for population identification, sometimes including alternative gating reagents, have been developed and implemented to monitor MRD in the setting of post targeted therapy.

Cytogenetic Risk Stratification of B-Acute Lymphoblastic Leukemia and Its Correlation with Other Prognostic Factors

Purpose of current study was to categorize WHO defined B-Acute Lymphoblastic Leukemia (B-ALL) cases into 3 cytogenetic risk groups (good, intermediate and poor) and to see their correlation with age, NCI risk criteria and treatment response. Clinical and diagnostic details were collected for 78 newly diagnosed B-ALL patients which included bone marrow morphology, flow cytometry immunophenotyping, karyotyping, FISH and RT-PCR. Study cohort comprised 44/78 (56.4%) children including 3 infants and 34/78 (43.6%) adults. Median age for paediatric group was 6 years (3 months-17 years) and for adults was 40.5 years (18 to 75 years). According to NCI risk criteria, excluding infants, 54 (72%) were high risk and 21 (28%) were standard risk. Clonal cytogenetic abnormality was detected in 59/78 cases (75.6%), while 19/78 (24.4%) cases showed normal karyotype. There was significant association of cytogenetic risk groups to age distribution (p value < 0.001) and NCI risk groups (p value < 0.001). There was no significant correlation of CNS involvement with cytogenetic risk groups (p = 0.064). Association of Day 8 steroid response and Day 15 bone marrow status with cytogenetic risk groups was significant (p = 0.006 and p = 0.003 respectively). Post treatment bone marrow status on Day 33 and Day 79 was available for 52 and 42 cases respectively. 9 adults died during induction phase. Day 33 post induction morphological remission was achieved in 51/52 cases (98%) and 1/52 (2.0%) were not in remission. Day 79 post induction morphological remission was achieved in 41/42 cases (98%) and 1/42 (2.0%) were not in remission. Day 33 or End of induction flow MRD (measurable residual disease) was negative in 39/52 (75.0%) patients and positive in 13/52 (25.0%) patients. Day 79 flow MRD was negative in 37/42 (88.1%) and positive in 5/42 (11.9%). Cytogenetic risk groups showed statistically significant Day 33 and Day 79 treatment response (morphologic remission: p = 0.009 and 0.003, flow MRD: p = 0.004 and p = 0.012 respectively). We concluded that cytogenetic risk groups showed statistically significant association with age, NCI risk criteria and treatment response.

Measurable Residual Disease Detection in B-Acute Lymphoblastic Leukemia: The Children's Oncology Group (COG) Method

Measurable (minimal) residual disease (MRD) in B-acute lymphoblastic leukemia (B-ALL), as assessed by flow cytometry, is an established prognostic factor used to adjust treatment in most pediatric therapeutic protocols. MRD in B-ALL has been standardized by the Children's Oncology Group in North America and more recently in a multicenter Foundation for the National Institutes of Health-funded study. This article outlines the reagents, instrument setup, and analysis protocols required for the reproducible detection of residual leukemic cells in patients following induction therapy for B-ALL. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Staining and flow cytometry for B-acute lymphoblastic leukemia (B-ALL) measurable residual disease detection Support Protocol: Specimen collection, handling, storage, and shipping Basic Protocol 2: Analysis and interpretation of data for B-ALL measurable residual disease detection Basic Protocol 3: Analysis of samples lacking sufficient CD19+ events.

UMAP Based Anomaly Detection for Minimal Residual Disease Quantification within Acute Myeloid Leukemia

Leukemia is the most frequent malignancy in children and adolescents, with acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) as the most common subtypes. Minimal residual disease (MRD) measured by flow cytometry (FCM) has proven to be a strong prognostic factor in ALL as well as in AML. Machine learning techniques have been emerging in the field of automated MRD quantification with the objective of superseding subjective and time-consuming manual analysis of FCM-MRD data. In contrast to ALL, where supervised multi-class classification methods have been successfully deployed for MRD detection, AML poses new challenges: AML is rarer (with fewer available training data) than ALL and much more heterogeneous in its immunophenotypic appearance, where one-class classification (anomaly detection) methods seem more suitable. In this work, a new semi-supervised approach based on the UMAP algorithm for MRD detection utilizing only labels of blast free FCM samples is presented. The method is tested on a newly gathered set of AML FCM samples and results are compared to state-of-the-art methods. We reach a median F1-score of 0.794, while providing a transparent classification pipeline with explainable results that facilitates inter-disciplinary work between medical and technical experts. This work shows that despite several issues yet to overcome, the merits of automated MRD quantification can be fully exploited also in AML.

Comparison of minimal residual disease measurement by multicolour flow cytometry and PCR for fusion gene transcripts in infants with acute lymphoblastic leukaemia with KMT2A gene rearrangements

This study aimed to evaluate the concordance between minimal residual disease (MRD) results obtained by multicolour flow cytometry (MFC) and polymerase chain reaction for fusion gene transcripts (FGTs) in infants with acute lymphoblastic leukaemia (ALL) associated with rearrangement of the KMT2A gene (KMT2A-r). A total of 942 bone marrow (BM) samples from 123 infants were studied for MFC-MRD and FGT-MRD. In total, 383 samples (40.7%) were concordantly MRD-negative. MRD was detected by the two methods in 441 cases (46.8%); 99 samples (10.5%) were only FGT-MRD-positive and 19 (2.0%) were only MFC-MRD-positive. A final concordance rate of 87.4% was established. Most discordance occurred if residual leukaemia was present at levels close to the sensitivity limits. Neither the type of KMT2A fusion nor a new type of treatment hampering MFC methodology had an influence on the concordance rate. The prognostic value of MFC-MRD and FGT-MRD differed. MFC-MRD was able to identify a rapid response at early time-points, whereas FGT-MRD was a reliable relapse predictor at later treatment stages. Additionally, the most precise risk definition was obtained when combining the two methods. Because of the high comparability in results, these two rather simple and inexpensive approaches could be good options of high clinical value.

An Extensive Quality Control and Quality Assurance (QC/QA) Program Significantly Improves Inter-Laboratory Concordance Rates of Flow-Cytometric Minimal Residual Disease Assessment in Acute Lymphoblastic Leukemia: An I-BFM-FLOW-Network Report

Simple Summary

Standardization of flow-cytometric assessment of minimal residual disease in acute lymphoid leukemia (ALL) is necessary to allow concordant multicentric application of the methodology. This is a prerequisite for internationally collaborative trials, such as the AIEOP-BFM-ALL and the ALL IC-BFM trial. We developed and applied a comprehensive training and quality control program involving a large number of international laboratories within the I-BFM consortium to complement standardization of the methodology with an educational component as well as with persistent quality control measures to allow large ALL treatment trials which use multi-laboratory FCM-MRD assessments for risk stratification of pediatric patients with ALL.

Abstract

Monitoring of minimal residual disease (MRD) by flow cytometry (FCM) is a powerful prognostic tool for predicting outcomes in acute lymphoblastic leukemia (ALL). To apply FCM-MRD in large, collaborative trials, dedicated laboratory staff must be educated to concordantly high levels of expertise and their performance quality should be continuously monitored. We sought to install a unique and comprehensive training and quality control (QC) program involving a large number of reference laboratories within the international Berlin-Frankfurt-Münster (I-BFM) consortium, in order to complement the standardization of the methodology with an educational component and persistent quality control measures. Our QC and quality assurance (QA) program is based on four major cornerstones: (i) a twinning maturation program, (ii) obligatory participation in external QA programs (spiked sample send around, United Kingdom National External Quality Assessment Service (UK NEQAS)), (iii) regular participation in list-mode-data (LMD) file ring trials (FCM data file send arounds), and (iv) surveys of independent data derived from trial results. We demonstrate that the training of laboratories using experienced twinning partners, along with continuous educational feedback significantly improves the performance of laboratories in detecting and quantifying MRD in pediatric ALL patients. Overall, our extensive education and quality control program improved inter-laboratory concordance rates of FCM-MRD assessments and ultimately led to a very high conformity of risk estimates in independent patient cohorts.

A Novel Method for the Evaluation of Bone Marrow Samples from Patients with Pediatric B-Cell Acute Lymphoblastic Leukemia-Multidimensional Flow Cytometry

Simple Summary

By supporting the selection of the most suitable treatment protocol, the advancement of diagnostic methods contributes to achieving the best possible outcome for pediatric cases of acute lymphoblastic leukemia (ALL). In this study, we focused on a novel possibility in the flow cytometric (FC) analysis, as this method is the initial, crucial step in the diagnostic algorithm of ALL and can determine further diagnostic and therapeutic strategies. After the retrospective, multidimensional dot-plot-based FC analysis of 72 bone marrow samples of children with ALL, we found that the integrated appearance of immunophenotype resulted in a simple, quick, and accurate method. Furthermore, associations between immunophenotype and cytogenetic alterations were detected, which enabled the identification of cases with potential adverse outcome by completing the conventional FC analysis with multidimensional dot-plots. Standardized multi-center studies would be required to validate our results.

Abstract

Multicolor flow cytometry (FC) evaluation has a key role in the diagnosis and prognostic stratification of ALL. Our aim was to create new analyzing protocols using multidimensional dot-plots. Seventy-two pediatric patients with ALL were included in this single-center study. Data of a normal BM sample and three BM samples of patients with BCP-ALL were merged, then all B cell populations of the four samples were presented in a single radar dot-plot, and those parameters and locations were selected in which the normal and pathological cell populations differed from each other the most. The integrated profile of immunophenotype resulted in a simple, rapid, and accurate method. There were no significant differences between the percentages of lymphoblasts in the detection of minimal residual disease (MRD) by multidimensional or conventional FC method (p = 0.903 at Day 15 and p = 0.155 at Day 33). Furthermore, we found associations between the position and the number of clusters of blast cells in the radar plots and cytogenetic properties (p = 0.002 and p < 0.0001 by the position and p = 0.02 by the number of subclones). FC analysis based on multidimensional dot-plots is not only a rapid, easy-to-use method, but can also provide additional information to screen cases which require detailed genetic examination.

Comparison of Two Quantitative PCR-Based Assays for Detection of Minimal Residual Disease in B-Precursor Acute Lymphoblastic Leukemia Harboring Three Major Fusion Transcripts

Two quantitative PCR (qPCR)-based methods, for clonal Ig or T-cell receptor gene (Ig/TCR) rearrangements and for fusion transcripts, are widely used for the measurement of minimal residual disease (MRD) in patients with B-precursor acute lymphoblastic leukemia (ALL). MRD of bone marrow samples from 165 patients carrying the three major fusion transcripts, including 74 BCR-ABL1, 54 ETV6-RUNX1, and 37 TCF3-PBX1, was analyzed by using the two qPCR-based methods. The coefficient correlation of both methods was good for TCF3-PBX1 (R² = 0.8088) and BCR-ABL1 (R² = 0.8094) ALL and moderate for ETV6-RUNX1 (R² = 0.5972). The concordance was perfect for TCF3-PBX1 ALL (97.2%), substantially concordant for ETV6-RUNX1 ALL (87.1%), and only moderate for BCR-ABL1 ALL (70.6%). The discordant MRD, positive for only one method with a difference greater than one log, was found in 4 of 93 samples (4.3%) with ETV6-RUNX1, 31 of 245 samples (12.7%) with BCR-ABL1, and 0 of TCF3-PBX1 ALL. None of the eight nontransplanted patients with BCR-ABL1-MRD (+)/Ig/TCR-MRD (-) with a median follow-up time of 73.5 months had hematologic relapses. Our study showed an excellent MRD concordance between the two qPCR-based methods in TCF3-PBX1 ALL, whereas qPCR for Ig/TCR is more reliable in BCR-ABL1 ALL.

Participation in the College of American Pathologists Laboratory Accreditation Program Decreases Variability in B-Lymphoblastic Leukemia and Plasma Cell Myeloma Flow Cytometric Minimal Residual Disease Testing: A Follow-up Survey

CONTEXT.—

Minimal residual disease (MRD) testing by flow cytometry is ubiquitous in hematolymphoid neoplasm monitoring, especially B-lymphoblastic leukemia (B-ALL), for which it provides predictive information and guides management. Major heterogeneity was identified in 2014. Subsequently, new Flow Cytometry Checklist items required documentation of the sensitivity determination method and required lower level of detection (LLOD) inclusion in final reports. This study assesses Laboratory Accreditation Program (LAP) participation and new checklist items' impact on flow cytometry MRD testing.

OBJECTIVES.—

To survey flow cytometry laboratories about MRD testing for B-ALL and plasma cell myeloma. In particular, enumerate the laboratories performing MRD testing, the proportion performing assays with very low LLODs, and implementation of new checklist items.

DESIGN.—

Supplemental questions were distributed in the 2017-A mailing to 548 flow cytometry laboratories subscribed to the College of American Pathologists FL3 Proficiency Testing Survey (Flow Cytometry-Immunophenotypic Characterization of Leukemia/Lymphoma).

RESULTS.—

The percentage of laboratories performing MRD studies has significantly decreased since 2014. Wide ranges of LLOD and collection event numbers were reported for B-ALL and plasma cell myeloma. Most laboratories determine LLOD by using dilutional studies and include it in final reports; a higher proportion of LAP participants used these practices than nonparticipants.

CONCLUSIONS.—

Several MRD testing aspects vary among laboratories receiving FL3 Proficiency Testing materials. After the survey in 2014, new checklist items were implemented. As compared to 2014, fewer laboratories are performing MRD studies. While LLOD remains heterogeneous, a high proportion of LAP subscribers follow the new checklist requirements and, overall, target LLOD recommendations from disease-specific working groups are met.

Monitoring minimal/measurable residual disease in B-cell acute lymphoblastic leukemia by flow cytometry during targeted therapy

B-cell acute lymphoblastic leukemia (B-ALL) is a hematologic malignancy of B-type lymphoid precursor cells. Minimal/measurable residual disease (MRD) is an important prognostic factor for B-ALL relapse. Traditional flow cytometry detection mainly relies on CD19-based gating strategies. However, relapse of CD19-negative B-ALL frequently occurs in patients who receive cellular and targeted therapy. This review will summarize the technical aspects of standard MRD assessment in B-ALL by flow cytometry, and then discuss the challenges of MRD strategies to deal with the scenario of CD19 negative or dim B-ALL relapse.

The genomic landscape of pediatric acute lymphoblastic leukemia and precision medicine opportunities

Acute lymphoblastic leukemia (ALL) is the most common childhood cancer and constitutes approximately 25 % of cancer diagnoses among children under the age of 15 (Howlader et al., 2013) [1]. Overall, about half of ALL cases occur in children and adolescents and it is the most common acute leukemia until the early 20s, after which acute myeloid leukemia predominates. ALL is the most successful treatment paradigm in pediatric cancer medicine as illustrated by the significant survival rate improvement from ∼10 % in the 1960s to >90 % today (Hunger et al., 2015) [2]. This remarkable success stems from the progressive improvement in the efficacy of risk-adapted multiagent chemotherapy regimens with effective central nervous system (CNS) prophylaxis via well-designed randomized clinical trials conducted by international collaborative consortia, enhanced supportive care measures to decrease treatment-related mortality, in-depth understanding of the genetic basis of ALL, and refinement in treatment response assessment through serial minimal residual disease (MRD) monitoring (Pui et al., 2015) [3]. These advances collectively contribute to a decline in mortality rate of 23.5% for children diagnosed with ALL in the US from 2000 to 2010 (Smith et al., 2014) [4]. Nevertheless, outcomes of older adolescents and young adults with ALL still lag behind those of their younger counterparts despite pediatric-inspired chemotherapy regimens (Stock et al., 2019) [5], relapsed/refractory childhood ALL is associated with poor outcomes (Rheingold et al., 2019) [6], and ALL still represents the leading causes of cancer-related deaths (Smith et al., 2010) [7]. The last two decades have witnessed important genomic discoveries in ALL, enabled by advances in next-generation sequencing (NGS) technologies to characterize the landscape of germline and somatic alterations in ALL, some of which have important diagnostic, prognostic and therapeutic implications. Comprehensive genomic analysis of large cohorts of children and adults with ALL has revised the taxonomy of ALL in the molecular era by identifying novel clonal, subtype-defined chromosomal alterations associated with distinct gene expression signatures, thus reducing the proportion of patients previously labelled as "Others" from 25 % to approximately 5 % (Mullighan et al., 2019) [8]. Insights into the genomics of ALL further provide compelling biologic rationale to expand the scope of precision medicine therapies for childhood ALL. Herein, we summarize a decade of genomic discoveries to highlight three different facets of precision medicine in pediatric ALL: 1) inherited predispositions of ALL; 2) relevant molecularly targeted therapies in genomically-defined ALL subtypes; and 3) treatment response monitoring via pharmacogenomics and novel MRD biomarkers.

Photoacoustic detection of circulating melanoma cells in late stage patients

Melanoma is the deadliest skin cancer and is responsible for over 7000 deaths in the US annually. The spread of cancer, or metastasis, is responsible for these deaths, as secondary tumors interrupt normal organ function. Circulating tumor cells, or those cells that spread throughout the body from the primary tumor, are thought to be responsible for metastasis. We developed an optical method, photoacoustic flow cytometry, in order to detect and enumerate circulating melanoma cells (CMCs) from blood samples of patients. We tested the blood of Stage IV melanoma patients to show the ability of the photoacoustic flow cytometer to detect these rare cells in blood. We then tested the system on archived blood samples from Stage III melanoma patients with known outcomes to determine if detection of CMCs can predict future metastasis. We detected between 0 and 66 CMCs in Stage IV patients. For the Stage III study, we found that of those samples with CMCs, 2 remained disease free and 5 developed metastasis. Of those without CMCs, 6 remained disease free and 1 developed metastasis. We believe that photoacoustic detection of CMCs provides valuable information for the prediction of metastasis and we postulate a system for more accurate prognosis.

Immunophenotypic shift in the B-cell precursors from regenerating bone marrow samples: A critical consideration for measurable residual disease assessment in B-lymphoblastic leukemia

Accurate knowledge of expression patterns/levels of commonly used MRD markers in regenerative normal-B-cell-precursors (BCP) is highly desirable to distinguish leukemic-blasts from regenerative-BCP for multicolor flow cytometry (MFC)-based measurable residual disease (MRD) assessment in B-lymphoblastic leukemia (B-ALL). However, the data highlighting therapy-related immunophenotypic-shift in regenerative-BCPs is scarce and limited to small cohort. Herein, we report the in-depth evaluation of immunophenotypic shift in regenerative-BCPs from a large cohort of BALL-MRD samples. Ten-color MFC-MRD analysis was performed in pediatric-BALL at the end-of-induction (EOI), end-of-consolidation (EOC), and subsequent-follow-up (SFU) time-points. We studied normalized-mean fluorescent intensity (nMFI) and coefficient-of-variation of immunofluorescence (CVIF) of CD10, CD19, CD20, CD34, CD38, and CD45 expression in regenerative-BCP (early, BCP1 and late, BCP2) from 200 BALL-MRD samples, and compared them with BCP from 15 regenerating control (RC) TALL-MRD samples and 20 treatment-naïve bone-marrow control (TNSC) samples. Regenerative-BCP1 showed downregulation in CD10 and CD34 expression with increased CVIF and reduced nMFI (p < 0.001), upregulation of CD20 with increased nMFI (p = 0.014) and heterogeneous CD45 expression with increased CVIF (p < 0.001). Immunophenotypic shift was less pronounced in the BCP2 compared to BCP1 compartment with increased CVIF in all but CD45 (p < 0.05) and reduced nMFI only in CD45 expression (p = 0.005). Downregulation of CD10/CD34 and upregulation of CD20 was higher at EOI than EOC and SFU time-points (p < 0.001). Regenerative-BCPs are characterized by the significant immunophenotypic shift in commonly used B-ALL-MRD markers, especially CD10 and CD34 expression, as compared to treatment-naïve BCPs. Therefore, the templates/database for BMRD analysis must be developed using regenerative-BCP.

Flow Cytometry Based MRD and Its Impact on Survival Outcome in Children and Young Adults with ALL: A Prospective Study from a Tertiary Cancer Centre in Southern India

Presence of minimal residual disease (MRD) following induction chemotherapy is a well-recognized risk factor to predict relapse in acute lymphoblastic leukemia (ALL). There is paucity of data on MRD and outcome in ALL from India. We share our experience in establishing a flow cytometry-based MRD assay for ALL with emphasis on determination of the number of patients who had MRD on day 35 of induction therapy and its correlation with outcome and other prognostic factors. We prospectively studied MRD in patients with ALL less than 25 years who achieved morphological complete remission with induction therapy. The initial series consisted of 104 patients with ALL. Ninety-two patients had bone marrow samples collected on day 35 of remission induction chemotherapy that was adequate for MRD. Strategy of monitoring MRD was based on flow cytometry using six color staining according the leukemia associated immunophenotype found at diagnosis. Data analysis was done using Fisher exact test. The median age was 8.5 years (range 0.9-22 years). Thirty-seven out of ninety-two patients (40.2%) had MRD at end of induction. MRD on day 35 was between 0.01 and 0.1% in 18.9% of patients, between 0.1 and 1% in 59.5% and more than 1% in 21.6% patients. Among the patients who had MRD, 16.7% had favourable cytogenetics, 60% had intermediate and 13.3% had high-risk cytogenetics. The presence or absence of residual leukemia by flow cytometry at day 35 was not significantly related to age (p = 1.0), male gender (p = 0.08) hyperleukocytosis (p = 0.25) or day 8 blast clearance (p = 0.21). However, T cell phenotype (p < 0.001) was significantly associated with MRD. The 5-year event free survival (EFS) for patients who had MRD versus those who did not was 69% and 61.1% respectively (p = 0.41). The 5-year overall survival (OS) for patients who had MRD versus those who did not was 72.5% and 61.1% respectively (p = 0.33). Flow cytometric techniques can be applied to monitor MRD in patients of ALL undergoing induction therapy. Our results suggest MRD correlates with certain known prognostic factors. Though the EFS and OS was lower in MRD positive patients, the results were not statistically significant probably because of the small sample size.

The influence of a dosage regimen of dexamethasone on detection of normal B-cell precursors in the bone marrow of children with BCP-ALL at the end of induction therapy

Minimal residual disease (MRD) monitoring by flow cytometry at the end of induction therapy is one of the key ways of a prognosis assessment in patients with acute lymphoblastic leukemia (ALL). In B-cell precursor ALL (BCP–ALL), this method of MRD detection is complicated due to the immunophenotypic similarity between leukemic cells and normal B-cell precursors (BCPs). A decrease in intensity of induction therapy can lead to a more frequent appearance of normal BCPs in the bone marrow, which significantly complicates the MRD monitoring. Aim: to assess the incidence of normal BCPs in bone marrow on the 36th day of induction therapy with two different regimens of glucocorticoid (GC) administration according to ALL-MB 2015 protocol. This study was approved by the Independent Ethical Committee and the Academic Council of Dmitriy Rogachev National Medical Research Center of Pediatric Hematology, Oncology, Immunology Ministry of Healthcare of Russian Federation. The study included 220 patients with BCP-ALL who were randomized to two types of GC-based induction therapy: a continuous administration of dexamethasone (n = 139) and an intermittent regimen with a 1-week dexamethasone therapy stop (n = 81). On the 36th day of induction therapy, MRD and normal BCPs were quantified in bone marrow samples by flow cytometry. On the 36th day of treatment, 43.2% of BCP(+) samples were established in the intermittent-therapy group, and 27.3% in the continuous-therapy group (p = 0.016). Comparison of the BCP level in BCP(+) samples revealed the more equitable distribution of BCPs at different developmental stages in the intermittent-therapy group, meanwhile mainly the immature BCPs in a quantity of less than 0.01% were found in the continuous-therapy group. Reduced-intensity induction therapy for patients with BCP-ALL leads to a noticeable increase of normal BCPs in bone marrow at the end of this treatment stage. A higher rate of BCP(+) bone marrow samples hinder the MRD detection due to the immunophenotypic similarity of BCPs and leukemic cells.

More precisely defining risk peri-HCT in pediatric ALL: pre- vs post-MRD measures, serial positivity, and risk modeling

Detection of minimal residual disease (MRD) pre- and post-hematopoietic cell transplantation (HCT) for pediatric acute lymphoblastic leukemia (ALL) has been associated with relapse and poor survival. Published studies have had insufficient numbers to: (1) compare the prognostic value of pre-HCT and post-HCT MRD; (2) determine clinical factors post-HCT associated with better outcomes in MRD+ patients; and (3) use MRD and other clinical factors to develop and validate a prognostic model for relapse in pediatric patients with ALL who undergo allogeneic HCT. To address these issues, we assembled an international database including sibling (n = 191), unrelated (n = 259), mismatched (n = 56), and cord blood (n = 110) grafts given after myeloablative conditioning. Although high and very high MRD pre-HCT were significant predictors in univariate analysis, with bivariate analysis using MRD pre-HCT and post-HCT, MRD pre-HCT at any level was less predictive than even low-level MRD post-HCT. Patients with MRD pre-HCT must become MRD low/negative at 1 to 2 months and negative within 3 to 6 months after HCT for successful therapy. Factors associated with improved outcome of patients with detectable MRD post-HCT included acute graft-versus-host disease. We derived a risk score with an MRD cohort from Europe, North America, and Australia using negative predictive characteristics (late disease status, non-total body irradiation regimen, and MRD [high, very high]) defining good, intermediate, and poor risk groups with 2-year cumulative incidences of relapse of 21%, 38%, and 47%, respectively. We validated the score in a second, more contemporaneous cohort and noted 2-year cumulative incidences of relapse of 13%, 26%, and 47% (P < .001) for the defined risk groups.

Clinical Significance of Minimal Residual Disease at the End of Remission Induction Therapy in Childhood Acute Lymphoblastic Leukemia

BACKGROUND

Detection of minimal residual disease (MRD) in the early phase of therapy is the most powerful predictor of relapse risk in children with acute lymphoblastic leukaemia (ALL).

AIM

We aimed to determine the significance of MRD at the end of remission induction therapy in the prediction of treatment outcome in children with ALL.

METHODS

Sixty-four consecutive patients aged 1-14 years with newly diagnosed ALL were enrolled in this study from January 2010 to October 2017. All patients were treated according to the ALL IC BFM 2002 protocol. MRD was detected at the end of remission induction therapy (day 33) by multiparameter 6-colour flow cytometry performed on bone marrow specimens with a sensitivity of 0.01%.

RESULTS

Overall, 42.2% of patients had detectable MRD on day 33 of therapy. MRD measurements were not significantly related to presenting characteristics but were associated with a poorer blast clearance on day 8 and 15 of remission induction therapy. Patients with negative MRD status on day 33 had a 5-year event-free survival of 94.6% compared with 76.1% for those with positive MRD status (P = 0.044).

CONCLUSION

MRD levels at the end of remission induction therapy measured by multiparameter flow cytometry have clinical significance in childhood ALL. High levels of MRD are strongly related to poor treatment outcome.

Automated Flow Cytometric MRD Assessment in Childhood Acute B- Lymphoblastic Leukemia Using Supervised Machine Learning

Minimal residual disease (MRD) as measured by multiparameter flow cytometry (FCM) is an independent and strong prognostic factor in B-cell acute lymphoblastic leukemia (B-ALL). However, reliable flow cytometric detection of MRD strongly depends on operator skills and expert knowledge. Hence, an objective, automated tool for reliable FCM-MRD quantification, able to overcome the technical diversity and analytical subjectivity, would be most helpful. We developed a supervised machine learning approach using a combination of multiple Gaussian Mixture Models (GMM) as a parametric density model. The approach was used for finding the weights of a linear combination of multiple GMMs to represent new, "unseen" samples by an interpolation of stored samples. The experimental data set contained FCM-MRD data of 337 bone marrow samples collected at day 15 of induction therapy in three different laboratories from pediatric patients with B-ALL for which accurate, expert-set gates existed. We compared MRD quantification by our proposed GMM approach to operator assessments, its performance on data from different laboratories, as well as to other state-of-the-art automated read-out methods. Our proposed GMM-combination approach proved superior over support vector machines, deep neural networks, and a single GMM approach in terms of precision and average F ₁ -scores. A high correlation of expert operator-based and automated MRD assessment was achieved with reliable automated MRD quantification (F ₁ -scores >0.5 in more than 95% of samples) in the clinically relevant range. Although best performance was found, if test and training samples were from the same system (i.e., flow cytometer and staining panel; lowest median F ₁ -score 0.92), cross-system performance remained high with a median F ₁ -score above 0.85 in all settings. In conclusion, our proposed automated approach could potentially be used to assess FCM-MRD in B-ALL in an objective and standardized manner across different laboratories. © 2019 International Society for Advancement of Cytometry.

Minimal residual disease status determined by multiparametric flow cytometry pretransplantation predicts the outcome of patients with ALL receiving unmanipulated haploidentical allografts

This study evaluated the effects of pretransplantation minimal residual disease (pre-MRD) on outcomes of patients with acute lymphoblastic leukemia (ALL) who underwent unmanipulated haploidentical stem cell transplantation (haplo-SCT). A retrospective study including 543 patients with ALL was performed. MRD was determined using multiparametric flow cytometry. Both in the entire cohort of patients and in subgroup cases with T-ALL or B-ALL, patients with positive pre-MRD had a higher incidence of relapse (CIR) than those with negative pre-MRD in MSDT settings (P < 0.01 for all). Landmark analysis at 6 months showed that MRD positivity was significantly and independently associated with inferior rates of relapse (HR, 1.908; P = 0.007), leukemia-free survival (LFS) (HR, 1.559; P = 0.038), and OS (HR, 1.545; P = 0.049). The levels of pre-MRD according to a logarithmic scale were also associated with leukemia relapse, LFS, and OS, except that cases with MRD <0.01% experienced comparable CIR and LFS to those with negative pre-MRD. A risk score for CIR was developed using the variables pre-MRD, disease status, and immunophenotype of ALL. The CIR was 14%, 26%, and 59% for subjects with scores of 0, 1, and 2-3, respectively (P < 0.001). Three-year LFS was 75%, 64%, and 42%, respectively (P < 0.001). Multivariate analysis confirmed the association of the risk score with CIR and LFS. The results indicate that positive pre-MRD, except for low level one (MRD < 0.01%), is associated with poor outcomes in patients with ALL who underwent unmanipulated haplo-SCT.

Flow-cytometric minimal residual disease monitoring in blood predicts relapse risk in pediatric B-cell precursor acute lymphoblastic leukemia in trial AIEOP-BFM-ALL 2000

BACKGROUND

Flow-cytometric monitoring of minimal residual disease (MRD) in bone marrow (BM) during induction of pediatric patients with acute lymphoblastic leukemia (ALL) is widely used for outcome prognostication and treatment stratification. Utilizing peripheral blood (PB) instead of BM might be favorable, but data on its usefulness are scarce.

PROCEDURE

We investigated 1303 PB samples (days 0, 8, 15, 33, and 52) and 285 BMs (day 15) from 288 pediatric ALL patients treated in trial AIEOP-BFM ALL 2000. MRD was assessed by four-color flow cytometry and evaluated as relative, absolute, and kinetic result.

RESULTS

In B-ALL only, PB measures from early time points correlated with relapse incidence (CIR). Best separation occurred at threshold <1 blast/μL at day 8 (5-year CIR 0.02 ± 0.02 vs 0.12 ± 0.03; P = 0.044). Patients with highest relapse risk were not distinguishable, but PB-MRD at days 33 and 52 correlated with prednisone response and postinduction BM-MRD by PCR (P < 0.001). Kinetic assessment did not convey any advantage. In multivariate analysis including day 15 BM-MRD, PB-MRD measures lost statistical power.

CONCLUSIONS

In summary, PB-MRD in pediatric B-ALL correlates with outcome and risk parameters, but its prognostic significance is not strong enough to substitute for BM assessment in AIEOP-BFM trials. It might, however, be valuable in treatment environments not using multifaceted risk stratification with other MRD measures.

Regenerative NanoOctopus Based on Multivalent-Aptamer-Functionalized Magnetic Microparticles for Effective Cell Capture in Whole Blood

Isolation of specific rare cell subtypes from whole blood is critical in cellular analysis and important in basic and clinical research. Traditional immunomagnetic cell capture suffers from suboptimal sensitivity, specificity, and time- and cost-effectiveness. Mimicking the features of octopuses, a device termed a "NanoOctopus" was developed for cancer cell isolation in whole blood. The device consists of long multimerized aptamer DNA strands, or tentacle DNA, immobilized on magnetic microparticle surfaces. Their ultrahigh sensitivity and specificity are attributed to multivalent binding of the tentacle DNA to cell receptors without steric hindrance. The simple, quick, and noninvasive capture and release of the target cells allows for extensive downstream cellular and molecular analysis, and the time- and cost-effectiveness of fabrication and regeneration of the devices makes them attractive for industrial manufacture.

Early (Day 15 Post Diagnosis) Peripheral Blood Assessment of Measurable Residual Disease in Flow Cytometry is a Strong Predictor of Outcome in Childhood B-Lineage Lymphoblastic Leukemia

BACKGROUND

In children with acute lymphoblastic leukemia (ALL) low levels of minimal residual disease (MRD) after induction, essentially assessed in the bone marrow, have been shown to be of good prognosis. However, only few studies have tested the peripheral blood for MRD.

METHODS

Here, we report the impact on survival of peripheral blood (PB) MRD assessment by multiparameter flow cytometry (MFC) at early time points of treatment in 125 B-ALL children, compared to Day 35 molecular bone marrow (BM) MRD. Patients were sampled for MFC one week postdiagnosis after a pre-phase of corticotherapy (Day 8), then after one week of chemotherapy (Day 15). The study enrolled 67 boys and 58 girls with a median follow-up of 52 months. Over the duration of the study, 20 patients relapsed and eight died. MFC was performed based on the leukemia-associated immunophenotype at diagnosis, using panels of 10 antibodies.

RESULTS

Although, PB MFC-MRD had no prognostic impact at Day 8, Day 15 MRD negativity was associated with a significantly better 4 years DFS (91.6 ± 3% vs. 67.6 ± 9% P = 0.0013). Furthermore, while MFC and molecular data were concordant in most cases, patients with detectable PB MRD on Day 15, yet negative in BM on Day 35 had a significantly lower DFS (P < 0.0001).

CONCLUSION

This study demonstrates that the less invasive procedure of MFC-MRD assessment in PB can be informative for childhood ALL patients at the early point of Day 15 of the treatment schedule. © 2019 International Clinical Cytometry Society.

Replacing cyclophosphamide/cytarabine/mercaptopurine with cyclophosphamide/etoposide during consolidation/delayed intensification does not improve outcome for pediatric B-cell acute lymphoblastic leukemia: a report from the COG

With modern chemotherapy, approximately 90% of patients with pediatric acute lymphoblastic leukemia are now cured. However, subsets of patients can be identified who remain at very high risk of relapse with expected 4-year disease-free survival rates <80%; such patients are appropriate candidates for intensive therapeutic strategies designed to improve survival. The AALL1131 trial was designed to determine, in a randomized fashion, whether substitution with cyclophosphamide/etoposide (experimental arm 1) would improve the 4-year disease-free survival of children, adolescents, and young adults with very high-risk B-cell acute lymphoblastic leukemia compared to a modified Berlin-Frankfurt-Münster regimen (control arm). Patients 1-30 years of age with newly diagnosed very high-risk B-cell acute lymphoblastic leukemia were randomized after induction in a 1:2 fashion to the control arm or experimental arm 1 in which they were given cyclophosphamide (440 mg/m² days 1-5)/etoposide (100 mg/m² days 1-5) during part 2 of consolidation and delayed intensification. Prospective interim monitoring rules for efficacy and futility were included where futility would be determined for a one-sided P-value ≥0.7664. The study was stopped for futility as the interim monitoring boundary was crossed [hazard ratio 0.606 (95% confidence interval: 0.297 - 1.237)] and the very high-risk arm of AALL1131 was closed in February 2017. Using data current as of December 31, 2017, 4-year disease-free survival rates were 85.5±6.8% (control arm) versus 72.3±6.3% (experimental arm 1) (P-value = 0.76). There were no significant differences in grade 3/4 adverse events between the two arms. Substitution of this therapy for very high-risk B-cell acute lymphoblastic leukemia patients on the Children’s Oncology Group AALL1131 trial (NCT02883049) randomized to cyclophosphamide/etoposide during part 2 of consolidation and delayed intensification did not improve disease-free survival.

Simple deep sequencing-based post-remission MRD surveillance predicts clinical relapse in B-ALL

Background

Next-generation sequencing (NGS) of the rearranged immunoglobulin heavy-chain gene has emerged as a highly sensitive method to detect minimal residual disease (MRD) in B acute lymphoblastic leukemia/lymphoma (B-ALL). However, a sensitive and easily implemented NGS methodology for routine clinical laboratories is lacking and clinical utility of NGS-MRD surveillance in a post-remission setting to predict clinical relapse has not been determined.

Methods

Here we described a simple and quantitative NGS platform and assessed its performance characteristics, quantified NGS-MRD levels in 122 B-ALL samples from 30 B-ALL patients, and explored the clinical merit of NGS-based MRD surveillance.

Results

The current NGS platform has an analytic sensitivity of 0.0001% with excellent specificity and reproducibility. Overall, it performs better than routine multi-color flow cytometry (MCF) in detecting MRD. Utilizing this assay in MRD surveillance in a post-remission setting showed that it detected conversion to positive MRD (CPMRD) in patients with NGS-based molecular remission much earlier than MCF, and that positive MRD conversion could be detected as early as 25.6 weeks prior to clinical relapse in closely surveilled patients. Post-remission CPMRD, but not NGS-based MRD positivity at end of induction, can accurately predict clinical relapse in our limited cohort of B-ALL patients.

Conclusions

This pilot proof-of-concept study illustrates the clinical utility of a simple, sensitive, and clinically feasible MRD detection platform in post-remission NGS-based MRD surveillance and early relapse detection in B-ALL patients.

Electronic supplementary material

The online version of this article (10.1186/s13045-018-0652-y) contains supplementary material, which is available to authorized users.

ETV6/RUNX1-positive childhood acute lymphoblastic leukemia (ALL): The spectrum of clonal heterogeneity and its impact on prognosis

The prognostic significance of the ETV6/RUNX1-fusion and of the accompanying aberrations is disputable; whether co-existing sub-clones are responsible for delayed MRD-clearance and thus, moderate outcome, remains to be clarified. We studied, in a paediatric cohort of 119 B-ALLs, the relation between the ETV6/RUNX1 aberration and the co-existing subclones with (a) presenting clinical/biological features, (b) early response to treatment(MRD) and (c) long-term outcome over a 12-year period. Patients were homogeneously treated according to BFM-based-protocols. 27/119 patients (22.7%) were ETV6/RUNX1-positive; 19/27 (70.4%) harbored additional genetic abnormalities while 9/19 (33.3%) presented with clonal heterogeneity. The most common abnormalities were del12p13 (37%), 3-6×21q22 (22.2%), del9p21 (18.5%) and 2-3xETV6/RUNX1 (18.5%). MRDd15-positivity (≥10-3) was detected in 44% of the cohort; the corresponding MRD among patients carrying subclones rises to 88.9%. Common features of all relapses were sub-clonal diversity, FCM-MRDd15-positivity and additional del(9p21) while there were no censored relapses among ETV6/RUNX1-positive patients with sole translocation and absence of additional aberrations, within a median follow-up time of 90 months. In our study, the presence of clonal heterogeneity and impaired FCM-MRD clearance among ETV6/RUNX1-positive patients, ultimately influenced prognosis. Longer follow-up is needed in order to further validate these initial results.

Flow cytometric minimal residual disease assessment of peripheral blood in acute lymphoblastic leukaemia patients has potential for early detection of relapsed extramedullary disease

OBJECTIVES

To evaluate peripheral blood (PB) for minimal residual disease (MRD) assessment in adults with acute lymphoblastic leukaemia (ALL).

METHODS

We analysed 76 matched bone marrow (BM) aspirate and PB specimens independently for the presence of ALL MRD by six-colour flow cytometry (FC).

RESULTS

The overall rate of BM MRD-positivity was 24% (18/76) and PB was also MRD-positive in 22% (4/18) of BM-positive cases. We identified two cases with evidence of leukaemic cells in PB at the time of the extramedullary relapse that were interpreted as MRD-negative in BM.

CONCLUSIONS

The use of PB MRD as a non-invasive method for monitoring of systemic relapse may have added clinical and diagnostic value in patients with high risk of extramedullary disease.

High-throughput sequencing for noninvasive disease detection in hematologic malignancies

Noninvasive monitoring of minimal residual disease (MRD) has led to significant advances in personalized management of patients with hematologic malignancies. Improved therapeutic options and prolonged survival have further increased the need for sensitive tumor assessment that can inform treatment decisions and patient outcomes. At diagnosis or relapse of most hematologic neoplasms, malignant cells are often easily accessible in the blood as circulating tumor cells (CTCs), making them ideal targets to noninvasively profile the molecular features of each patient. In other cancer types, CTCs are generally rare and noninvasive molecular detection relies on circulating tumor DNA (ctDNA) shed from tumor deposits into circulation. The ability to precisely detect and quantify CTCs and ctDNA could minimize invasive procedures and improve prediction of clinical outcomes. Technical advances in MRD detection methods in recent years have led to reduced costs and increased sensitivity, specificity, and applicability. Among currently available tests, high-throughput sequencing (HTS)-based approaches are increasingly attractive for noninvasive molecular testing. HTS-based methods can simultaneously identify multiple genetic markers with high sensitivity and specificity without individual optimization. In this review, we present an overview of techniques used for noninvasive molecular disease detection in selected myeloid and lymphoid neoplasms, with a focus on the current and future role of HTS-based assays.

Impact of post-transplant minimal residual disease on the clinical outcome of pediatric acute leukemia

This retrospective study examined the clinical significance of FCM-MRD in 36 patients with ALL and 29 patients with AML after their first allogeneic HSCT. Hematological (FCM-MRD ≥5.0%) and molecular relapse (FCM-MRD <5.0%) were first detected in 10 and two patients with ALL and in seven and eight patients with AML, respectively. Eight of 10 patients with molecular relapse eventually progressed to hematological relapse, although most were treated with immunological intervention by aggressive discontinuation of immunosuppressive therapy or donor lymphocyte infusion. Among these 12 patients, four of seven patients that obtained MRD^neg CR following post-transplant chemotherapy remain alive and disease-free after their second HSCT; however, all five patients who underwent a second HSCT in non-CR died of disease or treatment-related complications. As the FCM-MRD monitoring system used in the current study was probably not sensitive enough to detect MRD, which could be elucidated by immunological intervention, more sensitive diagnostic tools are mandatory for post-transplant MRD monitoring. Additional studies are required to address the impact of presecond transplant MRD on the clinical outcome of second HSCT.

Expression of Coagulation Factor XIII Subunit A Correlates with Outcome in Childhood Acute Lymphoblastic Leukemia

Previously we identified B-cell lineage leukemic lymphoblasts as a new expression site for subunit A of blood coagulation factor XIII (FXIII-A). On the basis of FXIII-A expression, various subgroups of B-cell precursor acute lymphoblastic leukemia (BCP-ALL) can be identified. Fifty-five children with BCP-ALL were included in the study. Bone marrow samples were obtained by aspiration and the presence of FXIII-A was detected by flow cytometry. G-banding and fluorescent in situ hybridization was performed according to standard procedures. The 10-year event-free survival (EFS) and overall survival (OS) rate of FXIII-A-positive and FXIII-A-negative patients showed significant differences (EFS: 84% vs. 61%, respectively; p = 0.031; OS: 89% vs. 61%; p = 0.008). Of all the parameters examined, there was correlation only between FXIII-A expression and 'B-other' genetic subgroup. Further multivariate Cox regression analysis of FXIII-subtype and genetic group or 'B-other' subgroup identified the FXIII-A negative characteristic as an independent factor associated with poor outcome in BCP-ALL. We found an excellent correlation between long-term survival and the FXIII-A-positive phenotype of BCP lymphoblasts at presentation. The results presented seem to be convincing enough to suggest a possible role for FXIII-A expression in the prognostic grouping of childhood BCP-ALL patients.

A QA Program for MRD Testing Demonstrates That Systematic Education Can Reduce Discordance Among Experienced Interpreters

BACKGROUND

Minimal residual disease (MRD) in B lymphoblastic leukemia (B-ALL) by flow cytometry is an established prognostic factor used to adjust treatment in most pediatric therapeutic protocols. MRD in B-ALL has been standardized by the Children's Oncology Group (COG) in North America, but not routine clinical labs. The Foundation for National Institutes of Health sought to harmonize MRD measurement among COG, oncology groups, academic, community and government, laboratories.

METHODS

Listmode data from post-induction marrows were distributed from a reference lab to seven different clinical FCM labs with variable experience in B-ALL MRD. Labs were provided with the COG protocol. Files from 15 cases were distributed to the seven labs. Educational sessions were implemented, and 10 more listmode file cases analyzed.

RESULTS

Among 105 initial challenges, the overall discordance rate was 26%. In the final round, performance improved considerably; out of 70 challenges, there were five false positives and one false negative (9% discordance), and no quantitative discordance. Four of six deviations occurred in a single lab. Three samples with hematogones were still misclassified as MRD.

CONCLUSIONS

Despite the provision of the COG standardized analysis protocol, even experienced laboratories require an educational component for B-ALL MRD analysis by FCM. Recognition of hematogones remains challenging for some labs when using the COG protocol. The results from this study suggest that dissemination of MRD testing to other North American laboratories as part of routine clinical management of B-ALL is possible but requires additional educational components to complement standardized methodology. © 2017 International Clinical Cytometry Society.

Significance of recurrence of minimal residual disease detected by multi-parameter flow cytometry in patients with acute lymphoblastic leukemia in morphological remission

We sought to determine the significance of minimal residual disease (MRD) relapse in patients with ALL after achieving MRD negative status following induction and consolidation therapy. Between January 2003 and September 2014, 647 newly diagnosed patients were treated [HyperCVAD-based (n = 531); Augmented BFM (n = 116)]. Six hundred and one (93%) achieved complete remission (CR), and 546 (91%) became MRD negative. Fifty-five patients [HyperCVAD-based (n = 49); Augmented BFM (n = 6)] developed recurrence of MRD while still in morphological CR and are the subjects of this study. MRD was assessed by 6-color (4-color prior to 2009) multi-parameter flow cytometry (MFC) at CR and multiple time points thereafter. Their median age was 44 years (range, 18-72 years), median WBC at initial presentation was 7.3 K/µL^-1 (range, 0.6-303.8 K/µL^-1 ) and median bone marrow blast percentage 88% (range, 26-98%). The median time to MRD relapse was 14 months (range 3-58 months). Forty-four (80%) patients subsequently developed morphological relapse after median of 3 months (range, <1-33 months) from detection of MRD recurrence. Treatments received after MRD positivity and prior to morphological relapse: 16 continued maintenance chemotherapy; 15 received late intensification; 9 allogeneic stem cell transplant, 9 changed chemotherapy, 6 no further therapy. Only six remain alive and in CR1 and nine are alive after morphological relapse. MRD relapse detected by MFC at any time after achieving CR is associated with a high risk for morphological relapse. SCT can result in long-term remission in some patients. Prospective studies of long-term MRD assessments, together with less toxic treatment strategies to eradicate MRD, are warranted.